As for a conventional non-contact IC card, there is proposed a structure in which capacity adjustment of a capacitor for setting the resonance frequency of a resonant circuit in an antenna mechanism is not required, mechanical damages to elements constituting a card are minimalized, and mass-productivity is increased. The structure has a plane coil which is connected to a non-contact IC chip and plural other plane coils which are arranged in the periphery thereof (Reference 1: Japanese Patent Laid-Open No. 2001-109861 and Reference 2: Japanese Patent Laid-Open No. 2001-109862). According to References 1 and 2, each of resonance frequencies is a frequency of high frequency electromagnetic field from a reader/writer device, a frequency shifted up/down to some extent, or the like, and several of the frequencies can be combined so as not to be interfered with one another, thereby obtaining broadband resonance properties.
There is an IC card in which a plurality of IC chips each using the same frequency and a booster coil are mounted on a base material of a card so as to expand a function of an IC card (Reference 3: Japanese Patent Laid Open No. 2003-331238). According to Reference 3, the IC chips use the booster coil as a common external antenna and thus, can individually conduct data communication with an external reader/writer.